In part one of this three-part post, we discussed how shutdowns could negatively affect lubricant film. For part two, we’ll reveal the impact of contamination on shutdown equipment.
Impact of Contamination on Shutdown Equipment
As mentioned in previous posts, contaminants enter machines during normal operation through vents, breathers, and shaft seals. When a machine is in steady state operation, the air inside the machine is warm and expanded, pushing air out of the headspace. However, the opposite effect happens when equipment is shutdown. It begins to cool and so does the air in the reservoir. The amount of space the air takes up shrinks, or reduces the air pressure causing your equipment to breathe in more air, increasing the risk of contamination.
Additionally, the cooler air will also begin to condense. This condensation introduces more water into your equipment increasing the risk of oxidation, a decrease in oil film strength, sludge and sediment buildup, etc. In fact, as little as 500 ppm or 0.05% by volume of dissolved water in a gear oil at 140° F will generate 300-400 ppm of free or emulsified water once the air cools to an ambient temperature of 50 or 60° F.
You might think that your equipment is at less risk of contamination when it is not running, but as you can see it may very well be at greater risk. Contamination control should not just be a focus of your equipment when in operation.